Several previous studies have demonstrated the successful incorporation of various functionalized oligomers into a sol-gel network to produce novel organic/hybrid materials referred to as "ceramers". References which describe such previous work include: Huang, H. et al., Macromolecules 1987, 20(6), 1322; Huang, H. et al., Polym. Bull., 14(6), 557 (1985). These initial studies involved a sol-gel reaction using tetramethylorthosilicate (TMOS) or tetraethylorthosilicate (TEOS) and silanol-terminated poly(dimethylsiloxane), for instance, under acidic conditions. The next systems investigated were hybrids based upon TEOS and TMOS, or related metal alkoxides, reacted with an oligomer of poly(tetramethylene oxide) endcapped with isocyanatopropyltriethoxysilane. The molecular weight of the oligomers was varied from 650 grams/mole to 2900 grams/mole. The silane-endcapped PTMO oligomers were also reacted with the silane under acidic conditions. The novel hybrid materials produced were monoliths with good mechanical properties and were optically clear.
The acids or bases typically employed in these sol-gel reactions for preparation of the ceramers, as well as conventional sol-gel ceramic materials, include hydrochloric acid (HC1) and glacial acetic acid. The presence of such species in the final material may lead to an accelerated aging effect. The ability of the chloride species to migrate in the material would also be expected to influence the ionic conductivity. in addition, there is a potential interest in fiber drawing or spinning applications for sol-gel derived materials.
A literature reference by K. Nakanishi et al. appears in J. Non-Crystalline Solids 108 (1989) 157-162, which speaks of the crystallization of silica gels containing sodium poly-4-styrene sulfonate which is not deemed to have functioned as a polymeric catalyst in such a system since the purpose of the sodium poly-4-styrene sulfonate was to initiate crystallization. In addition, a mineral acid was added to catalyze the sol-gel reactions instead of utilizing a polymeric acid catalyst.